In many integrated circuit applications, semiconductor chips are arranged in a packaging assembly. A packaging assembly allows for an electrical connection between the semiconductor chip and other devices via a printed circuit board, for example. Additionally, a packaging assembly protects the chip and the electrical connections from damage. Depending on the application, the packaging assembly may be exposed to potentially damaging environmental conditions, such as extreme temperature variations, high amounts of moisture and dust particles. For this reason, packaging assemblies include a protective covering that covers the semiconductor chip and the electrical connections. The protective covering is formed from a durable material to provide a robust seal that repels moisture and particles.
Packaging assemblies for MEMs (micro-electromechanical systems) technology require additional design considerations. In MEMs technology, a sensor device having a cantilever shape (i.e. anchored at only one end) is commonly arranged on the surface of the semiconductor chip. The sensor device may be used to measure environmental parameters such as, temperature, pressure, sound, composition of atmosphere, acceleration, etc. Thus, while the rest of the assembly may require protection from the exterior environment, these sensors require at least partial exposure to the exterior environment to measure these environmental parameters. Accordingly, a packaging structure in a MEMs application may require an opening in the protective covering to expose the MEMs sensor device.
The dual goal of exposing a MEMs sensor device to the exterior environment while protecting the rest of the components is not ideally accommodated by known packaging techniques. One known packaging technique involves molding a protective covering around the semiconductor chip. An encapsulant material is poured into a mold cavity and hardened. However, this technique is limited with respect to the kinds of shapes that can be formed. For instance, certain angles and corners may not be possible because the encapsulant hardens before it reaches the point of the mold cavity corresponding to the desired shape.